Diffusion measurements of isopentane, 1‐hexene, cyclohexane in polyethylene particles by the intelligent gravimetric analyzer

Abstract

AbstractThe diffusion coefficients of isopentane (i‐C5H12), 1‐hexene (C6H12), cyclohexane (C6H14) in polyethylene particles were measured by a highly sensible microbalance—intelligent gravimetric analyzer, using the desorption method with N2 as a bypassing gas. Both the effective diffusion coefficients (Deff) and dilute diffusion coefficients ( $D_{{\rm{eff}}}^\sim $) were measured simultaneously. It was found that $D_{{\rm{eff}}}^\sim $ was about one magnitude smaller than Deff and the logarithmic form of $D_{{\rm{eff}}}^\sim $ was linear with that of Deff. In addition, the effects of particle size and distribution, polymer properties (e.g., the crystallinity and melt index), and operating conditions (e.g., temperature and pressure) on Deff were systematically investigated. The results showed that Deff increased linearly with the increase of the square of particle size. The diffusion behaviors of hydrocarbons in polyethylene are of great importance in the polymerization and purging processes. © 2010 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013